There is a known semiconductor circuit wherein a spiral pattern is formed on a semiconductor substrate by using a thin film forming technology and this pattern is utilized as a coil.
FIG. 7 is a diagram showing a specific embodiment of the coil formed on the semiconductor substrate. As shown in FIG. 7, a spiral coil 110 is formed with a metal pattern (thin film pattern of copper or gold for instance) on a surface of a semiconductor substrate 100. It is possible, by forming the coil 110 on the surface of the semiconductor substrate 100, to integrally form all the components such as an oscillator including the coil on the semiconductor substrate 100 and eliminate externally mounted components. It is thereby possible to reduce the number of components and simplify processes so as to significantly reduce cost.
Incidentally, in the case of forming the coil 110 on the semiconductor substrate 100 as mentioned above, there is a problem that a high inductance cannot be secured because a diameter of the coil 110 cannot be extended. There is also a problem that, as the semiconductor substrate exists immediately under the coil 110, an eddy current is generated on the surface of the semiconductor substrate and so a high Q value cannot be obtained.